Running job at startup (boot time) You need to use special string called @reb

Running job at startup (boot time)

You need to use special string called @reboot. It will run once, at startup after reboot command.

@reboot /path/to/job @reboot /path/to/shell.script @reboot /path/to/command

This is an easy way to give your users the ability to run a shell script or command at boot time without root access. First, run crontab command:
$ crontab -e
OR
# crontab -e -u UserName
# crontab -e -u vivek
Run a script called /home/vivek/bin/installnetkit.sh
@reboot /home/vivek/bin/installnetkit.sh

Start crond automatically at boot time

You also need to enable crond service via sys v / BSD init style system. Under RHEL / CentOS / Fedora, you need to use chkconfig (ntsysv) command to enable crond on boot:
# chkconfig crond on
## Commands to start/stop/restart crond ###
# service crond restart
# service crond start
# service crond stop
Under Debian / Ubuntu Linux use update-rc.d as follows to turn on service on boot:
# update-rc.d cron defaults
If you are using modern distro with systemd, try
# systemctl enable crond.service
### this to start/stop/restart crond on systmd enabled distro such centos 7.x/debian/ubutnu/arch ###
# systemctl start crond.service
# systemctl stop crond.service
# systemctl restart crond.service
# systemctl status crond.service

Save and close the file. For further information read out tutorial on cron jobs.